Multiple Choice
What role does the sigma factor of RNA polymerase have in transcription?
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15. Gene Expression
Introduction to Transcription
Multiple Choice
Which of the following statements best describes the termination of transcription in bacteria?
A
Termination requires the addition of a 5' cap to the mRNA, signaling RNA polymerase to stop.
B
Termination occurs when RNA polymerase reaches the end of the chromosome.
C
Termination occurs when RNA polymerase encounters a specific DNA sequence that forms a hairpin loop in the RNA, causing the polymerase to dissociate.
D
Termination is initiated by the binding of ribosomes to the mRNA, which signals the end of transcription.
Verified step by step guidance1
Understand the process of transcription in bacteria: Transcription is the synthesis of RNA from a DNA template, carried out by RNA polymerase. It involves three main stages: initiation, elongation, and termination.
Focus on the termination stage: In bacteria, transcription termination occurs when RNA polymerase encounters specific signals in the DNA sequence that instruct it to stop synthesizing RNA.
Learn about the two main mechanisms of termination in bacteria: (1) Rho-dependent termination, which involves the Rho protein binding to the RNA and causing RNA polymerase to dissociate, and (2) Rho-independent termination, which involves the formation of a hairpin loop in the RNA followed by a stretch of uracil residues, destabilizing the RNA-DNA hybrid and causing RNA polymerase to release.
Analyze the statement about the hairpin loop: The correct answer describes Rho-independent termination, where a specific DNA sequence leads to the formation of a hairpin structure in the RNA. This structure disrupts the interaction between RNA polymerase and the DNA template, causing transcription to terminate.
Eliminate incorrect options: (1) The addition of a 5' cap is a feature of eukaryotic mRNA processing, not bacterial transcription termination. (2) RNA polymerase does not stop at the end of the chromosome; termination is sequence-specific. (3) Ribosome binding occurs during translation, not transcription termination.
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